He has been married 3 times. From 1953 to 1963 he was married to Ann Peri, with whom he had two daughters. From 1963 to 1977 he was married to Susan Willans, with whom he had a son and daughter. Since 1977 he has been married to philosopher Lynn Joy, who is also on the Philosophy faculty at Notre Dame.

MacIntyre's approach to moral philosophy has a number of complex strains that inform it. Although his project is largely characterised by an attempt to revive an Aristotelian conception of moral philosophy as sustained by the virtues, he nevertheless describes his own account of this attempt as a "peculiarly modern understanding" of the task.[4]

This "peculiarly modern understanding" largely concerns MacIntyre's approach to moral disputes. Unlike some analytic philosophers who try to generate moral consensus on the basis of an ideal of rationality, MacIntyre presents a historical narration of the development of ethics to illuminate the modern problem of "incommensurable" moral notions—i.e., notions whose value can not be reduced to a common measure. Following Hegel and Collingwood he offers a "philosophical history" (which he distinguishes from both analytical and phenomenological approaches to philosophy) in which he concedes from the beginning that "there are no neutral standards available by appeal to which any rational agent whatsoever could determine" the conclusions of moral philosophy.[5]

Indeed, one of MacIntyre's major points in his most famous work, After Virtue, is that the failed attempt by various Enlightenment thinkers to furnish a final universal account of moral rationality led to the rejection of moral rationality altogether by subsequent thinkers such as Charles Stevenson, Jean-Paul Sartre, and Friedrich Nietzsche. On MacIntyre's account, it is especially Nietzsche's utter repudiation of the possibility of moral rationality that is the outcome of the Enlightenment's mistaken quest for a final and definitive argument that will settle moral disputes into perpetuity by power of a calculative reason alone and without use of teleology.[6]

By contrast, MacIntyre is concerned with reclaiming various forms of moral rationality and argumentation that claim neither ultimate finality nor incorrigible certainty (the mistaken project of the Enlightenment), but nevertheless do not simply bottom out into relativistic or emotivist denials of any moral rationality whatsoever (according to him, the mistaken conclusion of Nietzsche, Sartre, and Stevenson). He does this by returning to the tradition of Aristotelian ethics with its teleological account of the good and moral persons, which was originally rejected by the Enlightenment and which reached a fuller articulation in the medieval writings of Thomas Aquinas. This Aristotelian-Thomistic tradition, he proposes, presents "the best theory so far," both of how things are and how we ought to act.

More generally, according to MacIntyre, it is the case that moral disputes always take place within and between rival traditions of thought that make recourse to a store of ideas, presuppositions, types of arguments and shared understandings and approaches that have been inherited from the past. Thus even though there is no definitive way for one tradition in moral philosophy to vanquish and exclude the possibility of another, nevertheless opposing views can call one another into question by various means including issues of internal coherence, imaginative reconstruction of dilemmas, epistemic crisis, and fruitfulness.[7]

Probably his most widely read work, After Virtue was written when MacIntyre was already in his fifties. Up until that time, MacIntyre had been a relatively influential analytic philosopher of a Marxist bent whose inquiries into moral philosophy had been conducted in a "piecemeal way, focusing first on this problem and then on that, in a mode characteristic of much analytic philosophy."[8] However, after reading the works of Thomas Kuhn and Imre Lakatos on philosophy of science and epistemology, MacIntyre was inspired to change the entire direction of his thought, tearing up the manuscript he had been working on and deciding to view the problems of modern moral and political philosophy "not from the standpoint of liberal modernity, but instead from the standpoint of ... Aristotelian moral and political practice."[9]

In general terms, the task of After Virtue is to account both for the dysfunctional quality of moral discourse within modern society and rehabilitate what MacIntyre takes to be a forgotten alternative in the teleological rationality of Aristotelian virtue ethics. MacIntyre's thought is revolutionary as it articulates a politics of self-defence for local communities that aspire to protect their practices and sustain their way of life from corrosive effects of the capitalist economy.[10]

MacIntyre's second major work of his mature period takes up the problem of giving an account of philosophical rationality within the context of his notion of "traditions," which had still remained under-theorized in After Virtue. Specifically, MacIntyre argues that rival and largely incompatible conceptions of justice are the outcome of rival and largely incompatible forms of practical rationality. These competing forms of practical rationality and their attendant ideas of justice are in turn the result of "socially embodied traditions of rational inquiry."[11] Although MacIntyre's treatment of traditions is quite complex he does give a relatively concise definition: "A tradition is an argument extended through time in which certain fundamental agreements are defined and redefined" in terms of both internal and external debates.[12]

Much of Whose Justice? Which Rationality? is therefore engaged in the task of not only giving the reader examples of actual rival traditions and the different ways they can split apart, integrate, or defeat one another (e.g. Aristotelian, Augustinian, Thomist, Humean) but also with substantiating how practical rationality and a conception of justice help constitute those traditions. MacIntyre argues that despite their incommensurability there are various ways in which alien traditions might engage one another rationally – most especially via a form of immanent critique which makes use of empathetic imagination to then put the rival tradition into "epistemic crisis" but also by being able to solve shared or analogous problems and dilemmas from within one's own tradition which remain insoluble from the rival approach.[13]

MacIntyre's account also defends three further theses: first, that all rational human inquiry is conducted whether knowingly or not from within a tradition; second, that the incommensurable conceptual schemes of rival traditions do not entail either relativism or perspectivism; third, that although the arguments of the book are themselves attempts at universally valid insights they are nevertheless given from within a particular tradition (that of Thomist Aristotelianism) and that this need not imply any philosophical inconsistency.

Three Rival Versions of Moral Inquiry was first presented by MacIntyre as part of the Gifford lecture series at the University of Edinburgh in 1988 and is considered by many the third part in a trilogy of philosophical argumentation that commenced with After Virtue. As its title implies, MacIntyre's aim in this book is to examine three major rival traditions of moral inquiry on the intellectual scene today (encyclopaedic, genealogical and traditional) which each in turn was given defence from a canonical piece published in the late nineteenth century (the Ninth Edition of the Encyclopædia Britannica, Nietzsche's Genealogy of Morals and Pope Leo XIII's Aeterni Patris, respectively). MacIntyre's book ultimately conducts a complex series of both interior and exterior critiques of the encyclopaedic and genealogical positions in an attempt to vindicate philosophical Thomism as the most persuasive form of moral inquiry currently on offer. His critique in chapter IX of Nietzsche's and Foucault's genealogical mode as implicitly committed to an emancipatory and continuous notion of self which they cannot account for on their own terms has been of particular influence.

While After Virtue attempted to give an account of the virtues exclusively by recourse to social practices and the understanding of individual selves in light of "quests" and "traditions," Dependent Rational Animals was a self-conscious effort by MacIntyre to ground virtues in an account of biology. MacIntyre writes the following of this shift in the Preface to the book: "Although there is indeed good reason to repudiate important elements in Aristotle's biology, I now judge that I was in error in supposing an ethics independent of biology to be possible."[14]

More specifically, Dependent Rational Animals tries to make a holistic case on the basis of our best current knowledge (as opposed to an ahistorical, foundational claim) that "human vulnerability and disability" are the "central features of human life" and that Thomistic "virtues of dependency" are needed for individual human beings to flourish in their passage from stages of infancy to adulthood and old age.[9] As MacIntyre puts it:

"It is most often to others that we owe our survival, let alone our flourishing ... It will be a central thesis of this book that the virtues that we need, if we are to develop from our animal condition into that of independent rational agents, and the virtues that we need, if we are to confront and respond to vulnerability and disability both in ourselves and in others, belong to one and the same set of virtues, the distinctive virtues of dependent rational animals"[15]

Engaging with scientific texts on human biology as well as works of philosophical anthropology, MacIntyre identifies the human species as existing on a continuous scale of both intelligence and dependency with other animals such as dolphins. One of his main goals is to undermine what he sees as the fiction of the disembodied, independent reasoner who determines ethical and moral questions autonomously and what he calls the "illusion of self-sufficiency" that runs through much of Western ethics culminating in Nietzsche's Übermensch.[16] In its place he tries to show that our embodied dependencies are a definitive characteristic of our species and reveal the need for certain kinds of virtuous dispositions if we are ever to flourish into independent reasoners capable of weighing the intellectual intricacies of moral philosophy in the first place.

MacIntyre is a key figure in the recent surge of interest in virtue ethics, which identifies the central question of morality as having to do with the habits and knowledge concerning how to live a good life. His approach seeks to demonstrate that good judgment emanates from good character. Being a good person is not about seeking to follow formal rules. In elaborating this approach, MacIntyre understands himself to be reworking the Aristotelian idea of an ethical teleology.

MacIntyre emphasises the importance of moral goods defined in respect to a community engaged in a 'practice'—which he calls 'internal goods' or 'goods of excellence'—rather than focusing on practice-independent obligation of a moral agent (deontological ethics) or the consequences of a particular act (utilitarianism). Before its recent resurgence, virtue ethics in European/American academia had been primarily associated with pre-modern philosophers (e.g. Plato, Aristotle, Thomas Aquinas). MacIntyre has argued that Aquinas' synthesis of Augustinianism with Aristotelianism is more insightful than modern moral theories by focusing upon the telos ('end', or completion) of a social practice and of a human life, within the context of which the morality of acts may be evaluated. His seminal work in the area of virtue ethics can be found in his 1981 book, After Virtue.

MacIntyre intends the idea of virtue to supplement, rather than replace, moral rules. Indeed, he describes certain moral rules as 'exceptionless' or unconditional. MacIntyre considers his work to be outside "virtue ethics" due to his affirmation of virtues as embedded in specific, historically grounded, social practices.[17]

Politically, MacIntyre's ethics informs a defence of the Aristotelian 'goods of excellence' internal to practices against the modern pursuit of 'external goods', such as money, power, and status, that are characteristic of rule-based, utilitarian, Weberian modern institutions. He has been described as a 'revolutionary Aristotelian' because of his attempt to combine historical insights from his Marxist past with those of Aquinas and Aristotle after his conversion to Catholicism. For him, liberalism and postmodernconsumerism not only justify capitalism but sustain and inform it over the long term. At the same time, he says, "Marxists have always fallen back into relatively straightforward versions of Kantianism or utilitarianism" and criticises Marxism as just another form of radical individualism, saying about Marxists, "as they move towards power they always tend to become Weberians." It is this reality of modern individualism in all its forms that gives MacIntyre's critique its urgency and power. Informed by this critique, Aristotelianism loses its sense of elitist complacency; moral excellence ceases to be part of a particular, historical practice in ancient Greece and becomes a universal quality of those who understand that good judgment emanates from good character. It has been argued that MacIntyre's thought is unable to provide a coherent and effective model for a justifiable and politically stable political order, due to its neglect of political theology.[18]

MacIntyre converted to Roman Catholicism in the early 1980s, and now does his work against the background of what he calls an "AugustinianThomist approach to moral philosophy."[19] In an interview with Prospect, MacIntyre explains that his conversion to Catholicism occurred in his fifties as a "result of being convinced of Thomism while attempting to disabuse his students of its authenticity."[20] Also, in his book Whose Justice, Which Rationality? there is a section towards the end that is perhaps autobiographical when he explains how one is chosen by a tradition and may reflect his own conversion to Roman Catholicism.[21] Parallel recent developments in the methods of philosophical research, which carry resonances with MacIntyre's take on Thomism are witnessed with a modern approach to Avicennism (the historical legacies that were built upon the philosophy of Avicenna; Ibn Sina) as embodied in the works of Nader El-Bizri in connection with Islam, even though the orientation is phenomenological instead of being analytic, and the focus is on ontology rather than moral philosophy.

Fuller accounts of MacIntyre's view of the relationship between philosophy and religion in general and Thomism and Catholicism in particular can be found in his essays "Philosophy recalled to its tasks" and "Truth as a good" (both found in the collection The Tasks of Philosophy) as well as in the survey of the Catholic philosophical tradition he gives in God, Philosophy and Universities.[22]